The Situation of Michael S. Gazzaniga

Everything was ready. The electrode was in place, threaded between the two hemispheres of a living cat’s brain; the instruments were tuned to pick up the chatter passing from one half to the other. The only thing left was to listen for that electronic whisper, the brain’s own internal code.

The amplifier hissed — the three scientists expectantly leaning closer — and out it came, loud and clear.

“We all live in a yellow submarine, yellow submarine, yellow submarine ….”

Dr. Gazzaniga, 71, now a professor of psychology at the University of California, Santa Barbara, is best known for a dazzling series of studies that revealed the brain’s split personality, the division of labor between its left and right hemispheres. But he is perhaps next best known for telling stories, many of them about blown experiments, dumb questions and other blunders during his nearly half-century career at the top of his field.

Now, in lectures and a new book, he is spelling out another kind of cautionary tale — a serious one, about the uses of neuroscience in society, particularly in the courtroom.

Brain science “will eventually begin to influence how the public views justice and responsibility,” Dr. Gazzaniga said at a recent conference here sponsored by the Edge Foundation.

And there is no guarantee, he added, that its influence will be a good one.

For one thing, brain-scanning technology is not ready for prime time in the legal system; it provides less information than people presume.

For another, new knowledge about neural processes is raising important questions about human responsibility. Scientists now know that the brain runs largely on autopilot; it acts first and asks questions later, often explaining behavior after the fact. So if much of behavior is automatic, then how responsible are people for their actions?

Who’s driving this submarine, anyway?

In his new book, “Who’s in Charge? Free Will and the Science of the Brain,” being published this month by Ecco/HarperCollins, Dr. Gazzaniga (pronounced ga-ZAHN-a-ga) argues that the answer is hidden in plain sight. It’s a matter of knowing where to look.

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He began thinking seriously about the nature of responsibility only after many years of goofing off.

Mike Gazzaniga grew up in Glendale, Calif., exploring the open country east of Los Angeles and running occasional experiments in his garage, often with the help of his father, a prominent surgeon. It was fun; the experiments were real attempts to understand biochemistry; and even after joining the Alpha Delta Phi fraternity at Dartmouth (inspiration for the movie “Animal House”), he made time between parties and pranks to track who was doing what in his chosen field, brain science.

In particular, he began to follow studies at the California Institute of Technology suggesting that in animals, developing nerve cells are coded to congregate in specific areas in the brain. This work was captivating for two reasons.

First, it seemed to contradict common wisdom at the time, which held that specific brain functions like memory were widely — and uniformly — distributed in the brain, not concentrated in discrete regions.

Second, his girlfriend was due to take a summer job right there near Caltech.

He decided to write a letter to the director of the program, the eminent neurobiologist Roger Wolcott Sperry (emphasizing reason No. 1). Could Dr. Sperry use a summer intern? “He said sure,” Dr. Gazzaniga said. “I always tell students, ‘Go ahead and write directly to the person you want to study with; you just never know.’ ”

At Caltech that summer after his junior year, he glimpsed his future. He learned about so-called split-brain patients, people with severe epilepsy who had surgery cutting the connections between their left and right hemispheres. The surgery drastically reduced seizures but seemed to leave people otherwise unaffected.